<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <script src="vue.js"></script>
    <title>Title</title>
</head>
<body>
<div id="box">
    <span v-text="msg"></span>
    <span v-html="msg1"></span>
    <span v-text="a"></span>
    <span v-text="b"></span>
</div>
</body>
<script>
    var app = new Vue({
        data: {
            msg: 'welcome',
            msg1:'<strong>welcome</strong>',
            a:1
        },
        computed:{
            b:{
                get:function () {
                    return this.a+1;
                },
                set:function (val) {
                   this.a = val;
                }
            }
        }
    });
    app.$mount('#box');
</script>
</html>